This invention is in the field of metal finishing and relates to internal deburring of metal parts. Cleaning, deburring, definning, descaling and polishing internal areas of cast or molded metal parts has been done by various means, all of which have certain disadvantages. Until the late 1960's internal deburring was done by hand held power tools, which was inefficient and labor intensive.
Attempts to automate internal deburring include electro-chemical deburring, thermal deburring, extrusion honing and resonant deburring. The electro-chemical method requires that an electrode-probe be placed at an exact distance from the burr to be removed from the part and a controlled electrical discharge be released to contact the burr. This process is usually performed in an electrolytic chemical solution. The electric discharge removes or reduces the size of the burr. This process is not time efficient and requires precision operation in order to be effective.
Thermal deburring processes use a high pressure chamber in which the metal parts are placed. The chamber is then filled with an explosive gas mixture which is then ignited. The controlled explosion knocks and burns the burrs and fins off the part. This process has limited utility because of equipment cost, limited size of parts which will fit in the chamber, and, to some extent, safety considerations. Thermal deburring, however, does provide treatment of several parts at once instead of requiring treatment of each part individually. The effectiveness is difficult to predict and control because different size, shape and thickness of burrs, fins and flashing may require different explosion temperatures and impact forces to remove them.
The extrusion honing process requires fixing the part to be deburred on a machine which then forces or extrudes through the internal passages of the part a heavy material, such as a silicone putty, containing abrasive particles. As the abrasive putty flows through the part removing the burrs and honing sharp edges. The part must then be thoroughly cleaned to remove the putty, abrasive and metal particles. The extrusion honing process is a low production process requiring expensive equipment.
The resonant deburring involves attaching metal parts to the ends of a large steel alloy beam, submerging the part in an abrasive media, and vibrating the beam at a harmonic or resonant frequency of the beam. The beam is vibrated by a power source at the center of the beam and is mounted to a frame at two points on the beam which are the null points on the beam when in resonant vibration. The resonant deburring is a relatively quick process for the actual deburring of a part. However, since resonant deburring generally treats only two parts at once it is a low production process. Resonant deburring has the further disadvantages of high noise level due to the high frequency vibration in the range 4,800 to 8,000 vibrations per minute, high maintenance, and is usually only practical for relatively large parts.
Thus, it is apparent that prior to this invention there is no process or apparatus which provides effective and satisfactory internal deburring of metal parts at high production rates.